Chapter 8: Force and Laws of Motion Case Study Questions | science Class 9 CBSE

ByteNotes

Chapter 8: Force and Laws of Motion Case Study Questions | science Class 9 CBSE | ByteNotes.in

Case Study

Passage with linked questions

Case Set

Case Set 1

Case Analysis

Passage

Rina placed a heavy wooden box on the floor and tried to push it gently, but it did not move. When she applied greater force, the box eventually started sliding. Her teacher explained the role of friction and unbalanced forces.

Question 1: Q1. Why didn't the box move when Rina pushed it gently?

A small applied force was balanced by the static friction force.
Friction acts in the opposite direction to resist motion.
When balanced, these forces cancel each other out, preventing motion.

Question 2: Q2. What caused the box to start moving later?

When Rina applied a greater force, it exceeded the maximum static friction.
The resulting unbalanced force caused the box to move.
Unbalanced force leads to change in the state of motion.

Question 3: Q3. What is an unbalanced force?

A force that is not completely opposed or canceled by another.
It causes acceleration or change in motion of an object.
If the net force is non-zero, the object experiences unbalanced force.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 2

Case Analysis

Passage

A marble rolls down one side of a smooth double-inclined plane and climbs up the other side to nearly the same height. When the second side is made less steep, it travels a longer distance but still reaches the same height.

Question 1: Q1. What conclusion did Galileo draw from this setup?

An object continues moving unless acted upon by an unbalanced force.
If there's no friction, it would roll forever trying to reach the same height.
This was the basis of Newton’s First Law of Motion.

Question 2: Q2. What happens if the second plane is made horizontal?

The marble continues rolling indefinitely at constant speed.
No unbalanced force acts on it; motion is sustained.
Demonstrates that uniform motion doesn’t need a net force.

Question 3: Q3. What does this demonstrate about the natural state of an object?

An object tends to remain in its state of motion or rest.
This tendency is called inertia.
Only an unbalanced force can change this state.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 3

Case Analysis

Passage

Ravi placed a coin on a card over a glass tumbler and flicked the card horizontally. The coin dropped straight into the glass.

Question 1: Q1. Why did the coin fall into the glass and not fly off?

The coin was at rest and resisted the change in state.
When the card was removed quickly, the coin stayed in place due to inertia.
Gravity then pulled it into the tumbler.

Question 2: Q2. What law of motion is demonstrated here?

Newton’s First Law of Motion.
An object at rest stays at rest unless acted upon by an unbalanced force.
Also known as the Law of Inertia.

Question 3: Q3. How does this relate to real-life scenarios?

Passengers lurch forward in a bus when brakes are applied.
Luggage topples during sudden stops if not tied properly.
Our body tends to remain in its previous state due to inertia.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 4

Case Analysis

Passage

A moving football is stopped by a player who gradually pulls his hands backward while catching it. His friend, who tried stopping the ball instantly, hurt his palms.

Question 1: Q1. Why does pulling hands backward reduce injury?

It increases the time over which momentum changes.
Reduces the rate of change of momentum.
Hence, the force felt by the palms is reduced.

Question 2: Q2. Which law does this illustrate?

Newton’s Second Law of Motion.
Force = Rate of change of momentum.
F = ma or F = (mv - mu)/t.

Question 3: Q3. What would happen if the ball was stopped instantly?

Change in momentum would happen in very short time.
Large force would act, causing pain or injury.
The impact force is inversely proportional to stopping time.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 5

Case Analysis

Passage

Two children standing on skateboards throw a heavy sandbag at each other. Each child moves backward after the throw or catch.

Question 1: Q1. Why do the children move in the opposite direction?

Due to the recoil caused by action and reaction forces.
Throwing or catching the bag exerts an equal and opposite force.
Demonstrates Newton’s Third Law of Motion.

Question 2: Q2. What happens to the motion if their masses are unequal?

Both feel equal force, but lighter child accelerates more.
Acceleration depends on mass: a = F/m.
Smaller mass → higher acceleration.

Question 3: Q3. How does this relate to daily activities?

Walking: foot pushes ground back, ground pushes foot forward.
Jumping off a boat makes it move backward.
Firing a gun causes recoil due to equal and opposite forces.

ByteNotes

Premium Access

Unlock all Case Study sets

You are viewing 5 free case study sets from this chapter. Upgrade to Premium to unlock the remaining 7 sets.

Upgrade to Premium7 questions locked

Chapter sections

Chapter 8: Force and Laws of Motion | Case Study Questions

Passage

Question 1: Q1. Why didn't the box move when Rina pushed it gently?

Question 2: Q2. What caused the box to start moving later?

Question 3: Q3. What is an unbalanced force?

Passage

Question 1: Q1. What conclusion did Galileo draw from this setup?

Question 2: Q2. What happens if the second plane is made horizontal?

Question 3: Q3. What does this demonstrate about the natural state of an object?

Passage

Question 1: Q1. Why did the coin fall into the glass and not fly off?

Question 2: Q2. What law of motion is demonstrated here?

Question 3: Q3. How does this relate to real-life scenarios?

Passage

Question 1: Q1. Why does pulling hands backward reduce injury?

Question 2: Q2. Which law does this illustrate?

Question 3: Q3. What would happen if the ball was stopped instantly?

Passage

Question 1: Q1. Why do the children move in the opposite direction?

Question 2: Q2. What happens to the motion if their masses are unequal?

Question 3: Q3. How does this relate to daily activities?

Unlock all Case Study sets